Hella Efficient Exterior Venetian Blinds

I noticed BuildingGreen added these exterior venetian blinds to the GreenSpec Directory recently. Hella exterior blinds are distributed in the U.S. through Savannah Trims and available in slat sizes of 2", 3.1", and 4". The blinds are aluminum, have lateral tension, and can be controlled manually or electrically. They're slick looking and come in a variety of heights, widths, and colors.

Like architectural mesh, and even more so, Hella exterior venetian blinds can reduce interior glare and heat gain, and thereby, improve the energy efficiency of a building and the performance of workers. The blinds can block up to 90% of incoming light. Plus, since the blinds are on the exterior of the building, any heat that is absorbed by the slats stays outside — no need to run mechanical systems to cool hot blinds.

Yeah, these are probably most effective in climates that have a fair amount of sun exposure. But Utah probably gets enough sun exposure to make tech such as this effective. Still trying to get pricing information, though.

I’ve seen tons of (older) homes with retractable metal awnings for southerly and westerly windows. Plus, many homes don’t have air conditioning (probably a swamp cooler), and if there are no plantation shutters or friendly overhangs or something else, exterior venetian blinds could be effective at keeping interior south/west spaces cool.

Retractable blinds can work in all climates.. in cold areas the can be retracted for a full view of the landscape and completely closed (mostly in the evenings ) to keep winds from buffering the glass and extracting more heat. Benefits in the South and West are enjoyed every day in any month. Denny

I think I would rather have the windows that harvest the energy rather than just block it. Also, there are windows with UV protection so that you get all of the ligth without as much of the glare, and with none of the harmful rays that you would get from the sunlight regularly.

Hello.. just a tip … when the blinds are almost perpendicular to the glass surface you have a good view as the blades bounce light into the room area from the ceiling. Excellent for working environments. Denny

I lived in Switzerland for three years and both my apartment and office building had blinds like this. These were new buildings which by the way had no air conditioning. It only gets really hot for about six weeks and the blinds make a big difference. People also used them for privacy rather than having heavy window treatments.

@Kersten Yes, these types of blinds have been far more succesful in Europe, although there are now a number of North American companies pushing this thin-blade, venetian style.

Even in a cold climate, however, shading is extremely effective. In Toronto, for example, even in January and February, there is actually a *cooling* demand in buildings because of heat radiating from lighting and human occupancy. If savings are possible there, you can imagine the potential in a place like Phoenix, AZ.

Interesting fact from my research/modeling: the annual savings realized by installing controllable solar shading on a 10 storey building in Toronto would be equivalent to the energy consumed by 63.4 average American homes.

@Preston – I have pricing and other information if you are interested (work with companies here and in Europe researching blinds and shading technology). Would be happy to help.

This fine article reveals one of the many methods and products available today. Other increasingly popular blade offerings are wood louvers, by SkyShield, in Cypress and Western Red Cedar. These offer the natural appearance of wood frequently expressed by architects and blended into the buildings facade. Dennis

GreenSpec also lists exterior shading systems from Hunter Douglas (Nysan), Industrial Louvers, Colt, Savannah Trims (Hella, Naco, and Skyshield), and a few others. Most of these units can be tied into automated building controls and solar tracking software to optimize performance. Alex Wilson talked with reps from Savannah Trims at Green Build. They are now offering a solar-powered motor option as well. As mentioned, many of the louver systems can be specified to work as lightshelves or to suit other daylighting needs. They truly can be fine tuned.

My husband and I are thinking of redecorating our house here in Indianapolis starting with the windows. I thought of putting blinds instead of curtains just so that we can control the room’s privacy, and the amount of light and air that goes in. All this time, I thought blinds are only for interior. These exterior blinds look cool!

Installing blinds for your window is a bright idea, especially if you want more control of your privacy. These blinds look really cool; and I might consider using them, once I’m decided to give my house a full makeover.

These external blinds look impressive and expensive. As they appear to roll up as well as rotate about the blind slat axis, they have to be robust to operate during all seasons even though they seem to be most useful in summer.
Some thoughts:
1) Like all louver slats, as they block sunlight, they also do some room darkening, depending on the angle of reflection. The more benefit to the a/c unit, the darker the room it appears.
2) Unless there is a sophisticated control algorithm, the blinds will probably produce non-optimal results. Like most blinds, they tend to be set and left that way for long periods of time.
3) Some of these blinds look like a security upgrade. That could be a plus.
4) The comment about setting the blinds perpendicular to the window is correct. Solar grates have this feature. Using selective reflectivity, the visible light is largely reflected and keeps the room bright while the infrared is largely absorbed and reduces the heat load to the a/c. Solar grates are much lower in cost and are designed for seasonal use. Maintenance is nil. The grate is “install and forget” and no operational adjusting is needed. The appearance from the curb changes while maintaining a view.
5) Alternatives to the impressive exterior blinds for the modest budget would include: solar screens, window films, awnings, solar grates, shutters, and shade trees.
I wonder if LBNL is including this design in its technical evaluation of window attachments?

These external blinds look impressive and expensive. As they appear to roll up as well as rotate about the blind slat axis, they have to be robust to operate during all seasons even though they seem to be most useful in summer.
Some thoughts:
1) Like all louver slats, as they block sunlight, they also do some room darkening, depending on the angle of reflection. The more benefit to the a/c unit, the darker the room it appears.
2) Unless there is a sophisticated control algorithm, the blinds will probably produce non-optimal results. Like most blinds, they tend to be set and left that way for long periods of time.
3) Some of these blinds look like a security upgrade. That could be a plus.
4) The comment about setting the blinds perpendicular to the window is correct. Solar grates have this feature. Using selective reflectivity, the visible light is largely reflected and keeps the room bright while the infrared is largely absorbed and reduces the heat load to the a/c. Solar grates are much lower in cost and are designed for seasonal use. Maintenance is nil. The grate is “install and forget” and no operational adjusting is needed. The appearance from the curb changes while maintaining a view.
5) Alternatives to the impressive exterior blinds for the modest budget would include: solar screens, window films, awnings, solar grates, shutters, and shade trees.
I wonder if LBNL is including this design in its technical evaluation of window attachments?